This invention relates to a reel shaft capable of engaging a reel hub of a tape cassette to give rotational force to the reel hub.
In general, a cassette tape recorder has a pair of reel shafts, which are rotated by a motor. The reel shafts individually engage a pair of reel hubs of a magnetic tape cassette to give rotational force to the reel hubs. Thus, a magnetic tape stretched between the reel hubs is wound on the reel hub on the take-up side without slack.
Conventionally, a reel shaft comprises a substantially cylindrical shaft body and a plurality of elongate projections formed on the outer peripheral surface of the shaft body. These projections are arranged at regular intervals along the circumferential direction of the shaft body, extending along the axial direction of the shaft body. Each reel hub has a plurality of engaging projections capable of engaging or meshing with the projections of the reel shaft. When the reel shaft is rotated after the reel hub is fitted on the reel shaft, the projections of the reel shaft engage the engaging projections of the reel hub to give rotational force to the reel hub. When the reel shaft is fitted into the reel hub, moreover, the extreme end faces of the engaging projections of the reel hub abut against the outer peripheral surface of the reel shaft, and the extreme end faces of the projections of the reel shaft abut against the inner peripheral surface of the reel hub. Thus, the reel shaft restrains the reel hub from moving in the directions normal to the axial direction of the reel shaft. However, the reel shaft cannot restrain the movement of the reel hub in the axial direction of the reel shaft. In a portable cassette tape recorder or a cassette tape recorder of a type in which a tape cassette is set upright, therefore, the reel hubs of the tape cassette are liable to move in the axial direction of the reel shafts, thereby causing irregular tape winding. The irregular tape winding would deteriorate tape feeding performance and/or cause wow or flutter.
These drawbacks are not peculiar to the reel shafts of cassette tape recorders, but are also found in those of video tape recorders, cinecameras, etc.